Techno-economic anaerobic co-digestion feasibility study for two-phase olive oil mill pomace and pig slurry

Anaerobic mono- (AmoD) and co-digestion (AcoD) of two-phase olive oil mill pomace (TPOP) and pig slurry (PS) at different ratios were studied in a semi-continuous stirred tank reactor (sCSTR) at mesophilic temperature (37 °C). The methane yields for AcoD experiments ranged from 150.9 to 274.3 L CH4 kg VS−1 d−1. The maximum chemical oxygen demand (COD) removal rate (59.60%) was achieved for TPOP/PS 80:20 w/w substrate composition at OLR 3.68 g VS Lreactor−1 d−1 and 24 days HRT. Despite the energy production from food waste is not a new process, the industrial implementation and application continue to be a challenge. Hence, the present paper also reports on the economic feasibility study of a full scale anaerobic co-digestion plant to treat 7000 t year−1 and 1750 t year−1 of TPOP and PS, respectively. The results of this study are compared against a conventional PS mono-digestion plant. Net present values (NPV) and payback time periods (PBT) were reported to be 782,493 € and 135,701 € and 6.7 and 9.2 years for AcoD and AmoD plants, respectively. Finally, the sensibility analysis concluded that AcoD configuration is less dependent on energy and compost sale prices variations.